Bioengineered devices for the arms have made significant advances in the rehabilitation of adults with nervous system injury. There is a surprising lack of adaptation of these devices for use in pediatric populations. This is especially troubling given the importance of early intervention and rehabilitation for optimal neurological and behavioral development. The proposed project joins experts from rehabilitation engineering, neonatology, and pediatric rehabilitation to test a novel device for intervention in infants with brain injury. The device is an enhanced pediatric version of the commercially available Wilmington Robotic Exoskeleton (WREX). The Pediatric WREX Plus (P- WREX+) can selectively assist or resist antigravity arm movements based on the needs of each individual. In the proposed 2-year study, 20 infants born with brain injuries and at high risk for significant neuromotor impairments will be followed using a multiple baseline single subject design. Infants will be assessed bi-weekly during a 1.5-month baseline, a 2-month intervention, and a 2- month post-intervention period. The assessments will include high-speed motion analysis and behavioral coding of infants' arm movement and function with and without the P-WREX+. We will capture these behaviors during spontaneous movement, a reaching task, and a functional object exploration task. During the intervention phase, infants wear the P-WREX+ during reaching and object exploration tasks. Aim 1 will determine how infants take advantage of the antigravity assistance provided by the P-WREX+ in the short-term to alter their upper extremity movement and function. Aim 2 will determine how intervention using the P-WREX+ impacts infants' upper extremity movement and function across the longer-term when they are not wearing the device. The proposed study is novel in its focus on very young, high-risk participants and in the introduction of a novel rehabilitation device with this population. It is a important first step in injecting engineering rehabilitation technology into early upper extremity rehabilitation. The results and experience from this initial study will generate both low-tech and high-tech applications for a variety of patient populations that will be the focus of future clinicl research, bioengineering, and commercial projects.